Microdispersions of photographic color couplers



United States. Patent MICRODISPERSIONS OF. PHOTOGRAPHIC COLOR COUPLERSLeopold Godowsky and Jerome J. Duane, Westport,

Conn., assignors to Eastman Kodak Company, Rochester, N. Y.,.acorporation of New Jersey No Drawing. Application December 23, 1955Serial No. 554,926

5 Claims. (CI. 96-97) This invention relates to color photographyandparticularly to a method for dispersing color couplers in photograpicemulsions. v

Photographic color couplers are either of the waterinsoluble type whichare dissolved in a hydrophobic solvent and dispersed in the photographicemulsionas described in Jelley and Vittum U. S. Patent 2,322,027, or

of the water solubilizable type which are dissolved in aqueous alkalinesolutions and mixed with the emulsion. The latter type containssolubilizing groups, .e. g., sulfonic' acid or carboxylic acid whichpermit formation of soluble .sodium or other water-soluble salts.

Unfortunately, all of these non-diffusing solubilized couplers have astrong tendency to react with gelatin when they are in solution, raisingthe viscosity of the mixtures. A large amount of gelatin compared to theweight of couplers must first be mixed with the alkaline solution of thecoupler before it on be mixed with a gelatino-silver halide emulsion.This increases the coating thickness or conversely decreases the dyedensity which can be obtained for a given coating thickness. A furtherdisadvantage of the solubilized couplers is that because of theirhomogeneous or continuous-nature in solution packets cannot be madesuccessfully from them by the method of Godowsky U. S. Patent2,698,794.. A certain proportion of soluble coupler remains free in theexternal or continuous'phase giving rise to color conphotographic dyeimages of higher contrast and maximum density than those usuallyobtained. Other objects will appear from the following description ofour invention;

These objects are accomplished by dissolving the acid form of a couplercontaining an acid group, e. g., carboxyl or sulfonic acid, in awater-soluble or water-misice cible solvent for the acid form of thecoupler, then adding water and a wetting or dispersing agent to thecoupler solution to form a microdispersion orsuspension of coupler intheaqueous medium. The water-soluble or watermiscible solvent is thenremoved and the coupler dispersion incorporated in a hydrophiliccolloidsilver halide emulsion. V i By microdispersion we mean anextremely finelydivided suspension or dispersion of the coupler;approaching a sol in degree of fineness. Mechanical grinding or millingis not required to attainthe fine particle size desired, but the solthat forms is a stable entity.

Couplers used in our process are color-formingcompounds capable ofcoupling with theoxidation product of a primary aromatic aminodeveloping agent on photographic de'velopment. Such couplers willbedescribed V more fully hereinafter.

- 7' Water-miscible solvents for the coupler used in our process includeacetone, methyl or ethyl alcohols, acetonitrile; dimethyl formamideanddioxane. I

The following couplers can be usedaccording to the process of ourinvention: f

-oH.-,oH err-onooo'om ooonooNncmomNnoo- (U. s. Patent 2,698,797, Example12 -on,-oH-on-- ont r N=C'-NHGOCaH-1 I (soon eonnm l 00-. H.

u. s. Patent-2,698,797, Example 14) Qoo'cmoomzG-oomoomz? CH3 7 s V i I 17 V i Q, (U. s; Patent 2,688,544, similar to Compound '1 oooon.

GONE

oooom OsHn V rHn (U. S. Patent 2,652,329, Compound 2 7 Other couplersdescribed in U. S. Patents 2,652,229, 2,688,544 and 2,698,227 'may beused in place of those .listed above.

3 The couplers of U. S. Patent 2,698,797 are resin couplers having therecurring structure where R'ishydrogen, phenyl, alkyL alkoxy,carboxyalkyl,

or, acyloxy, x and y are or 1,"R' represents a colorforming groupincluding anaryl group, capable of reacting with the oxidation productof a primary aromatic "amino' developing agent on photographicdevelopment,

*a'n'd'R is hydrogen or an alkylradical, e. g., methyl or ethyl.

' Example 1 This example describes'the preparation of a couplerdispersion from a cyan resin coupler.

Twenty grams of coupler No. 1 were dissolved by warmin to 50 in' arnixtureof450 cc. "of acetone and 50' cc. of water. of Alkaterge-C(substituted-oxa zoline) was added'and the solution c ooledfto roomtemperature (75 F.). To this One cc. of faf-1% acetone solution solutionthere was addedby' pouring in rapidly'without further stirring, 160 cc.of/waiter containing'0.1 cc. of

Aerosol OT (dioctyl e'ster'bf sodiumsul'fosuccinic acid).

A turbid suspension of coll'oidally dispersed coupler formedimmediately. The particles were barely resolvable under the microscopeat 900 'timesmagnification.

The suspension wasleft exposed to air at room temperature' for 24 hoursatwhic h timethevolu'rne'had reduced to 200 cc. with only a minimumamount of acetone left in "it. This corresponds to a solidsconcentration. No further stabilization was required and. the dispersioncould be stored at roomitemperatures up to 85 F. for over a year withoutevidence of crystallization, coalescence or sedimentation.

Example 2 This example describes a dispersion of a magenta resincoupler.

Fifteen=gramsof'coupler No. 2 were dissolved in 450 cc. of anacetone-water solution containing 90% acetone. Three cc. of a 1% acetonesolution of 'Alkaterge-C were added-"and the solutionliltered to remove'undissolved material. A solution of 150 cc. of water containing 0.2 cc.of Aerosol OT solution was poured intothe coupler solution to "form' an'iicrodispersion. Acetone was removed by room temperature evaporationover three days.

The final volume of microdispersion was 150 cc.

Example 3 'This example describes a dispersion ofayellowresin coupler.

Ten grams of coupler No. 3 were dissolvedain 200 cc. of a solution ofacetone and water, 90% of which was acetone, without heating. One cc. ofa 1% acetone solution of Alkaterge-C wasraddedfollowed by 100 cc. ofdistilled water added without further stirring. Acetone .was removed byevaporation and the final volume of the dispersion was 100 cc.

Example 4 h d.o a uumaumr. h d... e with :31. H "several days.Atan-coloied' solid was"ob'tain'e'd.

ghtlyjaid water, then fdried"atroornfternperature' for Five gramsof thisdicarboxylic acid were dissolved in 200 cc. of acetone by warming to 40C. for 10 minutes with rapid stirring. The solution was filtered clearof a small amount of insoluble residue and 0.1 cc. of a 1% acetonesolution of 'Alkaterge-C was added. The solution was cooled to 25 C. and500 cc. of distilled water was poured in rapidlyto form a turbidcolloidal dispersion of very small particles. This dispersion was leftexposed to the air overnight in a large evaporating dish in order toremove the acetone. To the residual aqueous suspension of 500 cc. total'volume there was added cc. of melted phthalic anhydride gelatin(prepared by reacting 20 grams of phthalic anhydride with 100 grams ofgelatin in the manner described in Ex ample 1 of Yutzy and Frame U. S.Patent 2,525,753) in 10% solution and the mixture stirred for 15minutes. This gelatin suspension was cooled to F. and l-N sulfuric acidwas added dropwise to reduce the'p'l-I to between 4.0 and 4.4 to causethe phthalic anhydride gelatin dispersion of coupler to flocculate.After settling for 4 hours, the water was decanted and the remainingsolid was'heated to 104 F. to coagulate the dispersion and'drive'oif'the remaining water. Ten cc. of a 10% solution of sodium citratewasadded and the mixture stirred at 104 F. in order to'raise the pH ofthe gelatin and redisperse the colloidalsuspension of coupler.

A quantity of 9.4'grams of this microdispersion' containing equal partsof the dicarboxylic acid and the phthalic anhydride; gelatin was dilutedwith 5% sodium citrate solution to'a volume of 30 cc. and a pH of about6.5. A silver chloride emulsion was made containing 80 grams ofgelatinper'mol of silver, and 4.3 cc. of the coupler dispersion weremixed with 10 cc. of the emulsion While stirring at 40 C. Nine grams ofa 20% solutionof hard gelatin'and 6 cc. of water were added *followed by0.5 cc. of7.5% .saponin solution and 0.3 cc.

of mucochloric acid solution. This volume of 30 cc. was'sprea'd overglass plates with an area of 140 square inches.

. In order to serve as a check, a quantity of the microdispersion of'coupler before adding the silver halide emulsion, was dissolved withsodium hydroxide to convert the acid to the sodium salt, then butteredwith "sodium citrate-'at a pH of about 8.5. Gelatin was then added forcoating and setting. A quantity of this coupler dispersion was mixedwith the silver halide emulsion as inthe case of theacid form of'the'coupl'er.

Both coatings were'expos'ed and processed in a devel oper bath of thefollowing composition:

2ainino+5-diethylarnino toluene HCl grams 2 Sodium sulfi' 2 jPotassiumbromidedo 2 liS'odiiim carbonate do 20 jBenzyl alcohol cc 10 Wa'ter tOliter" 1 i This example describes "the preparation of a dispersion Uponcomparing the acid microdispersion with the sodium salt dispersion, wefound that the color density produced by the acid microdispersion wasslightly higher than that produced by the dispersion of sodium salt ofthe coupler and that the dye image of the acid microdispersi'on morenearly corresponded to the tone reproduction curve of the developedsilver image.

Example 5 V for 30 minutes, diluted to 4 00 cc. with distilled water andl grarniof'sodium sulfite was fadded. fThe solutionwas left"standing"'overnight to insure 'complete hydrolysis.

tion with hydrochloric acid and filtering as described in Example 4.

Five grams of the dicarboxylic acid were dissolved in acetone anddispersed in the same manner as described in Example 4. Soon after thesuspension formed, 1-0 cc. ,of a 5% aqueous solution of polyvinylpyrrolidone was added as a stabilizing agent to minimize coalescenceduring the removal of acetone.

The dispersion was incorporated in a silver chloride emulsion asdescribed in Example 4 and comparison 'with a dispersion of the sodiumsalt of the coupler indicated satisfactory color reproduction.

Example 6 This example describes a dispersion of cyan resin couplerpackets.

. Twenty grams of coupler No. 1 were dissolved by warming to 50 C. in350 cc. of a mixture of 90% of acetone and of water, 1 cc. of a 1%acetone solution of Alkaterge-C was added andthe solution filteredclear. To this solution there was added by pouring in rapidly withoutfurther stirring, 200 cc. of distilled water containing a few drops ofdilute Aerosol OT solution. Acetone was evaporated from this solution byheating to 40 C. The final volume was 250 cc. equivalent to 8% couplerconcentration. 6.25 cc. of this dispersion was stirred together with 12cc. of a 10% solution of gelatin (melting point 182 to 400 F.) at 40 C.To this solution there Was added, in order, 6.4 grams of a silverchlorobromide emulsion (80 mol percent chloride) which had beenredsensitized, 10 cc. of water and 12 cc/of the copolymer ofmethyl-a-methacrylate and methacrylic acid at pH 8. After "stirring for5 minutes, 2.2 cc. of the ammonium salt of styrene-maleic anhydrideresin in 5% aqueous solution were added and the mixture stirredmechanically for 25 minutes duringwhich time packets were formed andhardened. A 10% calcium acetate solution,

2 cc., was added, followedby 5 cc. melted 20% hard gelatin. The mixtureappeared as an excellent dispersion of packets less than 4 microns indiameter.

Example 7 This example describes a dispersion of magenta resin couplerpackets.

A packet dispersion was made as in Example 6, using 8.3 cc. of a 9%aqueous micro dispersion of coupler No. 2 and 6.4 grams of agreen-sensitized silver chlorobromide emulsion.

Example8 This exampledescribes a mixed packet coating. A mixed packetcoating was formed by mixing 7.5 grams of the cyan packet emulsion ofExample 6 with 5.8 grams of the magenta packet emulsion of Example Thisexample describes a dispersion of non-resin cyan coupler packets.

Adispe'rsion was made by dissolving 6.6 grams of the of distilled waterwere added followedby 10 cc. of a 5% aqueous solution of polyvinylpyrrolidone. The acetone was allowed to evaporate by leaving thesuspension exposed to air overnight. To the dispersion there was thenadded 66 grams of melted 10% phthalic anhydride gelatin solution and thewhole dispersion diluted to 1000 cc.

while stirring during one hour. After cooling to 60 F.,

1 cc. of l-N sulfuric acid was added slowly to flocculate the phthalicanhydride gelatin. Water was removed by decantation and the residueredispersed by stirring at 40 C. with 10 cc. of a 10% sodium citratesolution. I

6.5 grams of the coupler dispersion were mixed with 5 grams of 20%phthalic anhydride gelatin at 40 C. and the mixture buffered with 2 cc.of 10% sodium citrate solution. A red-sensitized gelatino-silverchloride emulsion containing one mol of silver in 2040 grams ofemulsion, 10.2 grams of the emulsion being used, was added and mixedwith the coupler dispersion with stirring during five minutes. Packetswere formed by adding 2.5 cc. of a 2% aqueous solution of the ammoniumsalt of styrenemaleic anhydride resin and stirring for .15 minutes. Thepackets were 'then stabilized with 2 cc. of a 10% calcium acetatesolution. An excellent dispersion .of small spherical packet-s resulted.I 1

Example 10 This example describes a dispersion of non-resin yellowcoupler packets.

Packets were formed from the microdispersion of Example 5 by mixing 7.6grams of the coupler dispersion with 10.1 grams of 20% phthalicanhydride gelatin, 4 cc. of a 10% sodium-citrate solution and 10 gramsof a gelatino-silver chlorobromide emulsion (2 mol percent chloride)containing one mol of silver in 999 grams of emulsion. Five cc. of a 2%aqueous solution of the am monium salt of styrene-maleic anhydride resinwere added andthe packets which formed were stirred for 15 minutes at 40C. Finally, 4 cc. of a 10% calcium acetate solution were added. A gooddispersion of spherical packets somewhat larger in diameter thanthe cyanpackets of Example 9 was obtained.

Example 11 This example describes the preparation of a packet coating ofcyan and yellow couplers.

The packet dispersions of Examples 9 and 10 were mixed and coated,exposed to a color chart and developed in the developer of Example 4. Atwo-color coating of satisfactory contrast was produced.

A three-color mixed packet coating using cyan, magenta and yellowcouplers was also made, and exposed and developed as above. Aphotographic record which showed free acid of coupler No. 4 (prepared asdescribed in Example 4) in 300 cc. of acetone with moderate heating. Tothis solution there was added 0.1 .cc, of a 1% solution of Alkaterge-Cand the solution filtered clear of av good separation of the threecolors was obtained.

Example 12 This example illustrates the preparation of a couplerdispersion without the use of a dispersing agent;

Two grams of the acid form of coupler No. 5 (formed by hydrolysis andsubsequent acid precipitation as described in Example 5) were dissolvedin cc. of acetone at room temperature, then insolubilized in the form ofan extremely finely divided microdispersion by' pouring in rapidly 200cc. of distilled water. Then 1 cc. of a 5% solution ofpolyvinyl'pyrrolidone was added and the acetone removed by evaporation.

While we have described our invention'as being applied to themicrodispersion of couplers containing acid groups, microd-ispersionsmay also be prepared by our method using oil-soluble couplers of thetype disclosed in Jelley and Vittum U. S. Patent 2,322,027. Compoundsother than couplers such as antistain agents and ultra-violet absorbersmay also be dispersed in gelatin by our method.

It will be understood that the examples included herein are illustrativeonly and that our invention is to be taken as hmited only by the scopeof the appended claims.

What we claim is:

l. The-methodaof making a dispersion in gelatin of a water-insolublecolor coupler-capable of couplingwith the oxidation product of a primaryaromatic amino developing agent and containing at least one carboxylgroup, which comprises dissolving said carboXyl-containing coupler in awater-miscible solvent for said coupler, then adding Water and adispersing agent to the solution of coupler and water-miscible solventuntil said coupler is precipitated as a dispersion, removing saidwatermiscible solvent from said dispersion, and incorporating thedispersion in gelatin.

2. The method of making a dispersion in gelatin of a water-insolublecolor coupler capable of coupling with the oxidation product of aprimary aromatic amino developing agent and containing at least onecarboxyl group, which comprises dissolving said carboXyl-containingcoupler in acetone, then adding water and a dispersing agent to thesolution of coupler and acetone until said coupler is precipitated as adispersion, removing said acetone fromsaid dispersion, and incorporatingthe dispersion in gelatin.

3'. The method of making a dispersion in gelatin of a water-insolublecolor coupler capable of coupling with the oxidation product of aprimaryaromatic amino developing agent and containing at least one carboxylgroup,; which comprises dissolving said carboxyl-containing coupler inacetone, then adding water and the dioctyl ester ofsodium sulfosuccinicacid to the solution of coupler-and acetone until said coupler isprecipitated as adispersion, removing said acetone from said dispersion,and incorporating the dispersion in gelatin.

4, The method of making a packet photographic emulsion which comprisesdissolving in a water-miscible solvent for the coupler, a couplercompound having the recurring structure RH RI! I -CH:((|JH)Cll (OH2)r-C- R s o 0 OH 0 ONHR where'Ris selected fr'om the class 'consistingofhydrogen,

phenyl, alkyl, alkoxy', carboxyalkyl and acyloxy radicals";

acid, and the ammonium salt of styrene-maleic anhydride copolymer, andstirring, the mixture until packets are formed" 5. The method of makinga dispersion of a water-' insoluble color coupler capable of couplingwith the oxidation'product of a primary aromatic amino developing agentand containing at least one carboxyl group, which comprises dissolvingsaid carboxyl containing coupler in a water-miscible solvent for saidcoupler, then adding water to the solution of coupler and water-misciblesolvent until said coupler is precipitated as a dispersion, and removingsaid water-miscible solvent from said dispersion.

References Cited in the file of this patent UNITED'STATES IATENTS2,280,722 Schneider et al. Apr. 21, 1942 2,304,940 Mannes et al. Dec 15,1942 2,322,027 Jelley et al. June 15, 1943 2,403,721 Jelley et al. July9, 1946 2,478,400 Jelleyret: al. Aug. 9, 1949 2,652,329 McCrossen et alSept. 15, 1953 2,698,794 Godowsky Jan. 4, 1 955

1. THE METHOD OF MAKING A DISPERSION IN GELATIN OF A WATER-INSOLUBLECOLOR COUPLER CAPABLE OF COUPLING WITH THE OXIDATION PRODUCT OF APRIMARY AROMATIC AMINO DEVELOPING AGENT AND CONTAINING AT LEAST ONECARBOXYL GROUP, WHICH COMPRISES DISSOLVING SAID CARBOXYL-CONTAININGCOUPLER IN A WATER-MISCIBLE SOLVENT FOR SAID COUPLER, THEN ADDING WATERAND A DISPERSING AGENT TO THE SOLUTION OF COUPLER AND WATER-MISCIBLESOLVENT UNTIL SAID COUPLER IS PRECIPITATED AS A DISPERSION, REMOVINGSAID WATERMISCIBLE SOLVENT FROM SAID DISPERSION, AND INCORPORATING THEDISPERSION IN GELATIN.